SEOUL, April 13 (Yonhap) -- North Korea warned Saturday that South Korea will face a "catastrophic situation" if a group of North Korean defectors sends anti-Pyongyang propaganda leaflets across the border as planned.

North Korean defectors and a Seoul-based civic organization have said they plan to release leaflets with anti-Pyongyang messages, often mixed with U.S. dollar bills, via balloon in the city of Paju on the late founding leader's birthday, which falls on Monday.

In a commentary article published on the Web site of Uriminzokkiri, Pyongyang's main Internet-based media and propaganda site, the communist country said a catastrophic situation would occur if the leaflets cross the border on the "Day of the Sun," the birthday of late leader Kim Il-sung.

"Such confrontational madness will only snap up the extraordinary alarm and ire of our army and people," it said, adding that the North would shell South Korean sites used to send propaganda leaflets.

Activists in the South have frequently sent propaganda leaflets across the border, condemning the autocratic North Korean regime and calling for an uprising against the leadership. The isolationist country is currently ruled by Kim Jong-un, the grandson of the country's founder Kim Il-sung.

Pyongyang has frequently threatened retaliation for the South's anti-regime propaganda activities, including the launching of leaflets, although no real actions have been taken place so far.

The North's warning came amid rising speculation that North Korea is poised to launch a medium-range ballistic missile from its east coast in defiance of the international community's condemnation.

U.S. Secretary of State John Kerry said on Friday in Seoul that the U.S. is ready to talk with the North but stressed that preconditions for any talks hinge on Pyongyang giving up its missile launch and nuclear ambitions.

Meanwhile, in a separate commentary published on the Web site on Saturday, the communist regime again blamed South Korea for the recent suspension of operations at the joint-venture industrial park in the North's border city of Kaesong.

The communist country said it will not approve of the Kaesong Industrial Complex, claiming that the current stalemate has been caused by the South as it believes Seoul has violated dignity and autonomy of North Korea.

The North pulled out tens of thousands of its workers from the complex in the western border city of Kaesong and hundreds of South Korean workers have returned to Seoul amid escalating tensions on the Korean Peninsula.

As of Friday, 235 South Korean nationals and one Chinese national were in Kaesong. The daily steady outflow comes as no replacement workers, food and manufacturing parts have reached the complex since last Wednesday when Pyongyang banned all traffic from the South, although the communist country has not stopped people from leaving.